DESCRIPTION (from applicant's abstract): Little information is presently available describing the process of early auditory intervention (fitting of amplification) and resultant auditory-based outcomes in young children. The long-term objective of this project is to investigate speech perception, speech production, and spoken language skills in children with hearing loss who have received early, accurate audiologic assessment and appropriate fitting of amplification. This project will also provide information on the process of accurate hearing loss estimation in infants as well as developmental changes in audition and ear structures and how these may relate to the amplification fitting process. A large group of infants identified with hearing loss in a neonatal hearing screening program will have hearing thresholds predicted by frequency-specific auditory brainstem response (ABR). These thresholds will be used with infant-appropriate prescriptive techniques for fitting and validation of amplification. Infants will be enrolled in parent-infant education and followed for up to four years. Young children not screened for hearing loss in the newborn period who are identified with hearing loss up to 2 years of age will also be fit with amplification and followed as subjects. Speech perception and speech production as well as spoken language will be assessed with age- appropriate measures at regular intervals. Important information that may influence the relationship between amplification and auditory outcomes, such as type and timing of educational intervention, cognitive status, parental involvement, socio-economic status and other medical conditions will be documented and used in data analysis. Primary aims of this study are to 1) determine the relationship(s) between age at time of optimized amplification fitting and degree of hearing loss with speech perception, speech production, and spoken language in children with hearing loss; and, 2) determine the time course of this development. Secondary aims are to establish the accuracy of audiometric threshold prediction in newborns using ABIR against standard behavioral audiometric thresholds obtained after 6 months of age, and to determine the extent of developmentally related changes in ear canal volume and resonance on hearing aid prescriptive targets.